Load and save commands for interpeter

I just had an idea that it would be cool if the Prothon command line had 
commands to load and save scripts. When you "save" it would turn your 
transcript into a valid Prothon program that you could run again or edit 
and run.

When you "load" it would read a script and execute each line one at a 
time, printing out the result as if you had typed it.

In general it would be cool if the command line had extra functions like 
"run" which would run a command in the operating system shell. Maybe 
with string interpolation...

No: I'm not giving you more work Mark. If you like it, you can just 
write the idea down to do it a year from now or never. ;)

  Paul Prescod